What Is Tyre ?
Tyre is that significant part of the vehicle which carries complete load of
it & is made of rubber mixed with other chemicals and vulcanized. The
tyre is fitted with steel plies & cords that provide strength to it. The
main parts of the tyre body are:
Spine
Spine is that part of the tyre which is directly in contact with the
ground.
Shoulder
Shoulder is the thicker part of tyre where the spine & side wall joins.
Bead Wire
Bead wire is that rigid part which is inelastic & inflexible and
provides strength to the fitment of tire on the rim. The type of tyre and
structure of bead rings used, determines the size of bead wire.
Side Wall
As the name suggests tire’s sidewall is that area of the tire which is
not in contact with the ground & is in between Shoulder & Bead wire.
Plies
The plies construct the body of the tyre, they are made up of several
layers of fabrics. The most commonly used fabric is polyester cord. In case
of Radial tyres the plies run perpendicularly to the tread whereas in case
of Bias tyres they are placed diagonally. Nowadays Radial tyres use steel
belt plies for more strength & rigidity. The plies are covered with
rubber so that they can easily bond with other components & seal the
air. More the number of plies more is the strength of tire counted.
Heel
Heel is that part of the tire which is in touch with the rim & it helps
tire to be tied right to the rim.
Main Functions Of Tyre
The most important functions performed by the tire are as follows:
- To provide full support to the load of the vehicle & resist heavy
weight carrying by it.
- To transfer the engine power of the vehicle to the wheels during the
curves & brakes.
- To direct the vehicle in all surface conditions.
- To provide comfort to the driver & vehicle by reducing the
roughness of the path & by providing cushioning effect.
- Effective in increasing the performance of the vehicle.
Tyre Manufacturing
Raw Material
The main raw materials of the tyre consist of natural rubber, synthetic
rubber, carbon black & oil. Natural rubber comprises more than 80% of
the raw material used. The rest of the material includes various kinds of
reinforced material, which includes compounds of filler substances, oil used
as plasticizer, some hardening & vulcanizing agents, various booster
chemicals & protective agents. On an average the tyre is being
manufactured from 20-30 different components.
Mixing
All the above mentioned raw materials are properly mixed in an internal
mixer, known as Banbury Mixer, at about 120 degree Celsius. The mixing of
all the components & chemicals enhances the rubber characteristics.
The compounding of rubber used in the passenger car tyre is different from
that used in truck tyre. Similarly the compound used for agricultural &
OTR tyres is also different.
Calendering
The steel cord or textile fabric is woven to create a complex textile which
is coated with the rubber film on both sides. Textiles like rayon, nylon and
polyester are used for making plies & casing. Steel cord is used for
introducing belts.
Tread & Sidewall Extrusion
The tread and sidewalls are constructed by forming two (or more) different
and specifically designed compounds into profiles by feeding the rubber
through an extruder. Extruders produce continuous lengths of tread rubber,
or sidewall rubber, which are then cooled and cut to specific lengths.
Bead Construction
The bead core is constructed by coating plated steel wires, which are wound
on a bead former by a given number of turns to provide a specific diameter
and strength for a particular tyre.
Tyre Building
Tyre makers assemble the components into green tyres using assembly
machinery or commonly called tyre building machine. Tyre building is
traditionally a two-stage process. Although modern tyre factories now use a
certain number of single-stage building machines, two-stage building is
still widely used, particularly for the more standard sizes.
When the components have been drawn onto the belt drum of an assembly
machine and the frame of a tyre has been set on the bulkheads of the
stretching machine, the machine’s loading wheel transfers the unity
formed by the surface and the belt onto the frame.
The frame is then pressurized and stretched to fuse with the
above-mentioned unity. This is how a green tyre is manufactured.
The "green tyre" has no tread pattern, no markings. It is simply
a bare rubber casing.
Curing
“Green Tyre” made is vulcanized at 120-200 degree Celsius in
curing press called Bagomatic curing Press. The high steam pressure
conducted into the curing pad inside the curing press presses the elastic
green tyre against the tread pattern and side texts inside the moulds,
giving the tyre its final appearance.
Rice pulp is used to generate steam for this process, and curing process is
carried on for 20-70 minutes depending upon the size of tyre being cured.
Trimming
This is the process of removal of excess rubber from the cured tyre on the
trimming machine.
Inspection
Before the tyre is allowed to go to the dispatch warehouse, it is inspected
both visually and electronically for quality and uniformity.
Attention is paid to any faults and defects with the appearance of the tyre
in the visual inspection. The machine measures the pattern as well as radial
throw and lateral force variation of the tyre.When a tyre has been
inspected, it will be tested, labeled and transferred to the warehouse for
delivery.
Reading Tyres
The information on the sidewalls of your existing tyres is the first
important step in selecting new tyres for your vehicle. It looks something
like 195/65R14 82 V. Having this information will make the selection of your
next set of tyres a lot quicker and easier.
Typical example: P195/65R14 82 V
- P – Passenger Car Tyre
- 195 - 195 millimeters nominal section width
- 65 - Sidewall height is 65% of tyre nominal section width
- R - Radial type
- 14 - Means it fits 14" diameter wheel
- 82 - Load index
- V - Rated to 149mph (Speed Index)
*A standard tyre has a sidewall height, which is 82% of tyre nominal
section width.
*Reducing the % of sidewall height to tread nominal section width (the
'aspect ratio') enables tyres to be wider and put more tread on the road.
*Aspect Ratio is the ratio of sidewall height to nominal section width.
What do all signs mean ?
Tyre Type
The ‘P’ written along with the size of the tyre signifies tyre
for ‘Passenger Car’. Similarly ‘LT’ for ‘Light
Truck’
Tyre Width
‘195’ in the above mentioned example signifies the tyre section
width in millimeters (mm) measured from sidewall to sidewall.
Aspect Ratio
Aspect ratio is defined as the ratio of section height of the tire to
section width.
Construction
“R” on the tyre sidewall denotes the Radial type of tyre.
Similarly “B” denotes the BIAS construction of tyre.
Rim Diameter
The value written after “R” is the wheel/rim diameter in inches.
M+S
In some tyres ‘M+S’ is Mud & Snow pattern.
Load Index
This signifies the maximum load in Pounds or Kilograms that a tyre can
support when properly inflated. Also the max load (Single/dual) is also
mentioned elsewhere on the tyre sidewall.
| Code |
Pounds |
Kilograms |
Code |
Pounds |
Kilograms |
Code |
Pounds |
Kilograms |
| 60 |
551 |
250 |
82 |
1047 |
475 |
104 |
1984 |
900 |
| 61 |
567 |
257 |
83 |
1074 |
487 |
105 |
2039 |
925 |
| 62 |
584 |
265 |
84 |
1102 |
500 |
106 |
2094 |
950 |
| 63 |
600 |
272 |
85 |
1135 |
515 |
107 |
2149 |
975 |
| 64 |
617 |
280 |
86 |
1168 |
530 |
108 |
2205 |
1000 |
| 65 |
640 |
290 |
87 |
1201 |
545 |
109 |
2271 |
1030 |
| 66 |
661 |
300 |
88 |
1235 |
560 |
110 |
2337 |
1060 |
| 67 |
677 |
307 |
89 |
1279 |
580 |
111 |
2403 |
1090 |
| 68 |
695 |
315 |
90 |
1323 |
600 |
112 |
2470 |
1120 |
| 69 |
717 |
325 |
91 |
1356 |
615 |
113 |
2536 |
1150 |
| 70 |
738 |
335 |
92 |
1389 |
630 |
114 |
2601 |
1180 |
| 71 |
761 |
345 |
93 |
1433 |
650 |
115 |
2679 |
1215 |
| 72 |
783 |
355 |
94 |
1477 |
670 |
116 |
2756 |
1250 |
| 73 |
805 |
365 |
95 |
1521 |
690 |
117 |
2833 |
1285 |
| 74 |
827 |
375 |
96 |
1565 |
710 |
118 |
2910 |
1320 |
| 75 |
853 |
387 |
97 |
1609 |
730 |
119 |
2999 |
1360 |
| 76 |
882 |
400 |
98 |
1653 |
750 |
120 |
3087 |
1400 |
| 77 |
908 |
412 |
99 |
1709 |
775 |
121 |
3197 |
1450 |
| 78 |
937 |
425 |
100 |
1764 |
800 |
122 |
3306 |
1500 |
| 79 |
963 |
437 |
101 |
1819 |
825 |
123 |
3418 |
1550 |
| 80 |
992 |
450 |
102 |
1874 |
850 |
124 |
3528 |
1600 |
| 81 |
1019 |
462 |
103 |
1929 |
875 |
125 |
3638 |
1650 |
Speed Index
The speed index is an alphabetical coding that represents the maximum speed
to be acquired by the vehicle. For example: ‘H’ means that the
tyre has the maximum speed of 130mph. One should note that it is NOT
recommended to exceed the speed limit of the vehicle beyond the speed rating
of the tyre. It may prove fatal.
| Code |
mph |
km/h |
Code |
mph |
km/h |
| A1 |
3 |
5 |
L |
75 |
120 |
| A2 |
6 |
10 |
M |
81 |
130 |
| A3 |
9 |
15 |
N |
87 |
140 |
| A4 |
12 |
20 |
P |
94 |
150 |
| A5 |
16 |
25 |
Q |
100 |
160 |
| A6 |
19 |
30 |
R |
106 |
170 |
| A7 |
22 |
35 |
S |
112 |
180 |
| A8 |
25 |
40 |
T |
118 |
190 |
| B |
31 |
50 |
U |
124 |
200 |
| C |
37 |
60 |
H |
130 |
210 |
| D |
40 |
65 |
V |
149 |
240 |
| E |
43 |
70 |
Z |
over 149 |
over 240 |
| F |
50 |
80 |
W |
168 |
270 |
| G |
56 |
90 |
(W) |
over 168 |
over 270 |
| J |
62 |
100 |
Y |
186 |
300 |
| K |
68 |
110 |
(Y) |
over 186 |
over 300 |
TWI
Tread wear Indicator (TWI) It is the marking located where the tread meets
the sidewall. When the tread wears & matches the TWI sign, it is
strongly recommended to replace the tyres of the vehicle or re-groove them
in time.
Other signs
- TL – Tubeless
- TT – Tube Type
- C – Stands for Commercial
- LL – Light load
- SL – Standard Load
- XL – Extra Load
- Arrows – shows the directional tires, that the tyre will perform
better when rotated in particular direction.
Tyre Age
Before 2000, in 1990’s it was believed that the tyre is manufactured
for the life of ten years, hence the old system follows the three digit
system in which the first 2 digits represents the week & the 3rd digit
represents the year. For example: ‘427’ means 42nd week of 7th
year of 1990’s (1997).
Since 2000, this 3 digit coding is replaced by 4 digit coding, whose first
2 digits represent the week & the next 2 digits represent the year. For
example: ‘4206’ means 42nd week of the year 2006
DOT
“DOT” means the tyre is complaint with all applicable safety
standards established by the U.S. Department Of Transportation (DOT). A
unique 12 digit serial number is followed by the DOT mark, which is a
combination of numbers and letters.
UTQG
“UTQG” stands for Uniform Tyre Quality Grading, a quality rating
system developed by the Department of transportation (DOT). DOT requires the
manufacturer to grade tyres based on three performance factors: Tread wear,
Traction and Temperature resistance.
Tread Wear
Better – More than 100
Baseline – 100
Poorer – Less than 100
The tread wear grade is based on a 7,200-mile wear test conducted under
controlled conditions on a specified government test track. The higher the
grade, the longer the expected tire life. Tread wear gradings are given in
numbers. For example: A tyre graded 200 would wear twice as long on the
government test track as one graded 100. The relative performance of tires
depends upon the actual conditions of their use, and may vary due to driving
habits, service practices, difference in road characteristics and climate.
Traction
A – Best
B – Intermediate
C – Acceptable
The rating is decided at the speed of 40 mph and represents the tyre
ability to stop on wet pavement as measured on specific government test
surfaces of asphalt and concrete. Due to rough surface & low speed, the
tread pattern does not play the vital role in test results. This test
neither indicates concerning ability of tyre, nor to resist hydroplaning.
Temperature
The temperature grades are also described in the same way as that for
traction. A (highest) grade, B being the intermediate & C being
acceptable. The rating represents the tyre’s resistance to the
generation of heat when tested under controlled conditions on a specified
indoor laboratory test wheel. Sustained high temperature can cause the
material of the tyre to degenerate tyre life and thus reduces tyre life.
Excessive tire temperature can lead to fatal tyre failure. The grade C
corresponds to a level of performance that all passenger car tires must meet
under the Federal Motor Vehicle Safety Standard No. 109. Grades A and B
represent higher levels of performance on the laboratory test wheel than the
minimum required by law.
Tyre Care & Safety
1). Road Conditions
Following operating conditions significantly influence tyre life both in
terms of wear & tear and structural durability.
- Rough/abrasive road surface.
- Paved road
- Straight road
- Broken up roads
- Hilly zigzag roads
- Unmade country roads
2). Driving Habits
Careful driving habits will ensure optimum tyre life, unavoidable damages
besides avoiding serious road accidents.
Over Speeding – This is the most common habit to drive at high speed
and sometimes over the recommended speed rating of the tyre. This results in
excessive heating of the tyre, faster wear & hence decrease in life of
tyre.
Quick acceleration & braking – Panic start & stop of vehicle
also decreases the life of tyre. Sudden acceleration builds up excessive
heat & sudden braking results in scrub off a good amount of tread rubber
causing faster wear of tyres.
Sharp turns around the corner – Excessive wear can happen from one
side of the tyre. One should slow down and take a smooth & slow turn.
Riding over stones & other piercing items – This is bad for the
tire structure and causes damage to the tyre plies inside. Try to avoid as
much as you can.
Parking on rough surface (pointed stone or bricks) – Always take care
of the surface where you are parking your vehicle. Long parking of tyres on
such surface causes damage to tyre. Be careful & try to avoid these type
of objects to come under the tyre.
Speeding over bad roads & speed breakers – Speeding your vehicle
over bad rough surface or over speed breakers causes serious damage to tyre
structure and ply. One should slow down on bad roads & speed breakers.
3). Seasonal Effect
1)A country experiences various climatic & weather conditions from
region to region, somewhere it is very dry & somewhere it is wet, hot &
cold, etc. This variation influences the tyre life in terms of mileage &
structural durability.
4). Tyre Pressure
- Tyre Pressure checks (including the spare tyre) must be done
regularly at least once in a weeks.
- Tyre pressure should be checked using an accurate pressure gauge.
- Tyre pressure should be checked when tyres are cold.
- In case of under inflation and over inflation, rapid tread wear and
premature tyre failures occur.
- Tyre pressure should always be maintained as per the vehicle
manufacturers’ recommendations, mentioned at information placard,
at door or in owner’s manual.
Below shown is the effect of over & under inflated tyre & accurate
inflated tyre conditions.
5). Wheel Alignment
1) Wheel alignment is the adjustment of the wheel angles in such a way that
all the four wheels are parallel to each other & perpendicular to the
ground. The primary function of wheel alignment is to enhance tyre
performance & its life. (Wheel alignment is completely different from
wheel balancing. Wheel balancing is the condition when weight of the wheel
is evenly distributed whereas wheel alignment is the condition when all the
four wheels are parallel to each other & perpendicular to the ground. If
wheel is not properly balanced, it causes vibration in the vehicle at high
speed, whereas if the wheel is not properly aligned it causes wear &
tear of tyres.)
To notice if the wheels are not aligned, one should concentrate on
following factors:
- Uneven wear & tear of tyres.
- Right or left pulling of steering wheel during driving.
- Wandering in the vehicle even when on a straight level road.
- Vibration of steering wheel.
Alignment involves the adjustment of vehicle’s suspension along with
wheels & tyres. There are many factors which are responsible for the
hampering of alignment. They are as follows:
Caster
Caster is the inclination of the steering pivot in the front or behind
direction, to adjust steerability. If the angle is in front then the caster
is positive and if it is behind then it is negative caster. Rear wheel drive
cars have positive caster and front wheel drive cars have negative caster.
Caster is there only for front wheels as only the front wheels steer.
Camber
Camber is the inward or outward inclination of the tyres when viewed from
front. If the top of the wheel is leaning inwards then the camber is
negative and if it is leaning outwards then the camber is positive. The
positive camber is present on the front tyres for them to stay in a straight
line when driving on a straight road. Rear tyres have zero camber.
Toe
Toe measurement is the difference of the lateral distance between the front
end of the front tyres and the rear end of the front tyres. Toe-in means
front end of the tyre is closer and in toe-out means front end of the tyre
is apart.
Ride Height
Ride height is the distance between the vehicle’s frame and the road.
During customization any change of measurement in the ride height can hamper
the alignment of the suspension and reduce tyre life as well as performance.
The chassis height of rear side is always kept more than that on the vehicle’s
front side.
Types of Wheel Alignment
There are basically three types of wheel alignment offered for the modern
wheels, which are as follows:
Front End Alignment: In this type, only the front wheels are aligned &
adjusted.
Thrust End Alignment: Here the alignment of rear wheels is done in
accordance to the centre line of the vehicle. If the thrust angle is zero
the steering wheel will not be centered and to adjust this thing first the
rear toe should be adjusted to the center line and then the front toe.
Four-Wheel Alignment: This is the most common type of alignment in which
all the four wheels are aligned & adjusted with respect to the
suspension.
Advantages of Wheel Alignment
- Reduces Tyre wear.
- Improves fuel efficiency of vehicle.
- Improves handling.
- Safer & more comfortable driving.
6). Tyre Rotation
Tire rotation is vital to achieve even tread wear and long tread life. With
the front tyres having some positive camber angle, the inner edge of the
tyre wears faster, hence swapping a front tyre with the diagonally opposite
rear tyre will increase the life of the tyre; the tyre which is now at the
rear will wear from the centre as the rear end has no camber. Rotate tires
at the vehicle manufacturer’s recommended intervals or at 5,000 - 7,000
miles if not specified.
7). Cleaning Tyres
To ensure that Hamilton Tyres give their best performance and look their
best, the user must use a mild soap or detergent and a semi-soft bristle
brush. To rinse use clean & plain water.
8). Tire Mounting
1)As tire mounting is a difficult process, it needs to be handled with
great care & by professional only. Kindly make sure that the tire
diameter matches the rim diameter. Note that the tire being mounted on the
rim is of the suitable application. There are some recommendations from
HAMILTON which are to be taken care while tire mounting:
- Do not apply bead sealer as this can inhibit the seating of the bead.
- The bead and tire rim surface needs to be lubricated before mounting.
- Lock assembly on mounting machine or place in safety cage.
- Always take care of the air pressure filled to seat the bead, never
exceed the limit.
- Do not use any volatile substance to help in seating of the bead.
9). Tyre Sizing
We strongly recommend that the tyres should be fitted as per the
recommendations mentioned on the vehicle manual. For best handling do not
mix radial tires with non radials. Mounting tires of different speed
ratings, sizes or construction could result in tyre failure. However if
tires of different profiles are to be used then note that the wider tires
fits to the rear of vehicle.
10). Tyre Wear
It is strongly recommended that the tyre needs replacement when only 2/32”
tread depth is remaining. All DOT approved tires in production have a tread
wear indicator molded into the tread pattern. This small piece of rubber
appears to be a bridge between two tire grooves, but is only 2/32” in
height. When the top of this indicator is even with the plain of the tread
pattern, the tires should be replaced. Failure to replace tires with tread
depths less than 2/32” could result in accidents due to loss of
traction.
